The present invention generally relates to refrigeration systems and, more particularly, to refrigeration systems having flow-control restriction or expansion devices incorporated therein.
A refrigeration system, such as a motor vehicle air conditioner, typically has a closed circuit through which a refrigerant undergoes a thermodynamic cycle. The circuit of a motor vehicle air conditioner typically includes an engine driven semi-hermetic compressor, a condenser connected in series to the compressor, a flow-control restriction or expansion device, which is often referred to as a flow-control valve or expansion valve, connected in series to the condenser, and an evaporator connected in series between the expansion device and the compressor. The compressor raises the pressure of xe2x80x9clow-pressurexe2x80x9d gaseous refrigerant to a pressure suitable for operation of the condenser. xe2x80x9cHigh-pressure hotxe2x80x9d gaseous refrigerant passes from the compressor to the condenser. The condenser condenses the high-pressure hot refrigerant by transferring heat from the refrigerant to the ambient environment or atmosphere located outside the motor vehicle. The expansion device causes the high-pressure liquid refrigerant exiting the condenser to experience a sudden pressure drop, causing the liquid refrigerant to cool and expand (usually a constant enthalpy process). The xe2x80x9clow-pressure coldxe2x80x9d liquid refrigerant passes to the evaporator where it vaporizes by absorbing heat from surrounding air and as a result cools the surrounding air. Typically, a fan or blower forces air across the evaporator and delivers xe2x80x9ccooledxe2x80x9d air to a passenger compartment of the motor vehicle. Low-pressure hot gaseous refrigerant exits the evaporator and returns to the compressor and the above-described thermodynamic cycle repeats as the refrigerant flows through the circuit.
Such motor vehicle air conditioning systems can be easily tailored for efficient cooling at specific driving conditions such as, for example, highway driving (constant speed) or city driving (stop and go). When tailored for efficient cooling at one driving condition, however, cooling efficiency can be less than desirable while at other driving conditions. One solution has been to incorporate an expansion valve operable between two different flow conditions. For example, U.S. Pat. No. 5,715,704 to Cholkeri et al., which is expressly incorporated herein in its entirety by reference, discloses an electronically-controlled expansion valve. The expansion valve is a high/low stage direct controlled solenoid valve. The solenoid operates the expansion valve between a high-flow state providing high or maximum refrigerant flow through he expansion valve and a low-flow state providing low or minimum refrigerant flow through the expansion valve. The solenoid is periodically energized to obtain the low-flow and de-energized to obtain the high-flow state in response to refrigeration system parameters and/or motor vehicle parameters such as, for example, head pressure, vehicle speed and engine rpm to provide more efficient cooling at various driving conditions.
While refrigeration systems with such expansion valves are effective at providing more efficient cooling at multiple driving conditions, the expansion, refrigeration systems cooling more than one compartment have a need for even greater control of the flow through the expansion valve. Accordingly, there is a need in the art for an improved refrigeration system having a flow-control valve.
The present invention provides a refrigerant flow-control operable between a no-flow condition and a flow condition which overcomes at least some of the above-noted problems of the related art. According to the present invention, a flow control valve includes a body having an inlet and an outlet and forming a refrigerant passageway extending from the inlet to the outlet. The passageway has a restriction and a valve flow passage adapted such that refrigerant flows through the valve flow passage and the restriction generally in series. The restriction is located upstream from the valve flow passage. A valve element is within the body and movable between a first position closing the valve flow passage to generally prevent refrigerant flow therethrough and through the passageway and a second position opening the valve flow passage to permit refrigerant flow therethrough and through the passageway. A biasing member is within the body and resiliently urges the valve element into the first position. A valve actuator is adapted to selectively move the valve element to the second position in response to a control signal supplied thereto.
According to another aspect of the present invention, the present invention provides a refrigerant flow-control valve operable between a no-flow condition and a flow condition. The flow-control valve includes a tubular-shaped body having an inlet and an outlet and forming a refrigerant passageway extending from the inlet to the outlet, a cylindrically-shaped restrictor secured within the tube and forming a restriction, and a cylindrically-shaped stop secured within the tube and forming a valve flow passage. The stop is downstream and spaced-apart from the restrictor and the restriction has a greater resistance to flow than the valve flow passage. A plunger is within the tube between the restrictor and the stop and carries a valve element. The plunger is movable between a first position closing the valve flow passage to generally prevent refrigerant flow therethrough and through the passageway and a second position opening the valve flow passage to permit refrigerant flow therethrough and through the passageway. A biasing member is within the tube and resiliently urges the valve element into the first position. A valve actuator is adapted to selectively move the valve element to the second position in response to a control signal supplied thereto.
According to yet another aspect of the present invention, the present invention provides a refrigeration system. The refrigeration system has a compressor, a condenser, and an evaporator connected in series and an expansion valve connected in series between the condenser and the evaporator. The refrigeration system includes a body having an inlet and an outlet and forming a refrigerant passageway extending from the inlet to the outlet. The passageway has a restriction and a valve flow passage adapted such that refrigerant flows through the valve flow passage and the restriction generally in series. The restriction is located upstream from the valve flow passage. A valve element is within the body and movable between a first position closing the valve flow passage to generally prevent refrigerant flow therethrough and through the passageway and a second position opening the valve flow passage to permit refrigerant flow therethrough and through the passageway. A biasing member is within the body and resiliently urges the valve element into the first position. A valve actuator is adapted to selectively move the valve element to the second position in response to a control signal supplied thereto.
According to yet even another aspect of the present invention, the present invention provides a method of delivering refrigerant from a high pressure region to a low pressure region of a refrigeration system through a variable dimension passageway to expand the refrigerant as it enters the low pressure region. The method includes the steps of: coupling the high and low pressure regions through a valve body having an inlet and an outlet and forming a refrigerant passageway extending from the inlet to the outlet. The passageway has a restriction and a valve flow passage downstream of the restriction and is adapted such that refrigerant flows through the valve flow passage generally in series with the restriction. A valve element is mounted within the valve body such that the valve element is movable between a first position closing the valve flow passage to generally prevent refrigerant flow therethrough and through the passageway and a second position opening the valve flow passage to permit refrigerant flow therethrough and through the passageway. The valve element is biased into the first position and is selectively moved to the second position by a valve actuator in response to a control signal supplied to the valve actuator.